混凝与电絮凝废水中多种金属离子协同沉淀机制研究

采用混凝和电絮凝工艺去除废水中的多种金属离子(Pb^2+、Cd^2+、Cu^2+、Ni^2+),研究混凝反应主要影响因素液相pH、混凝剂(PAC)投加量对各金属离子去除效率的影响,探讨废水pH、施加电流密度对各金属离子电絮凝去除效率的影响,阐明混凝和电絮凝多金属协同沉淀去除的机制。结果表明,PAC混凝去除废水中Pb^2+、Cd^2+、Cu^2+、Ni^2+的最佳pH为7.0,最佳投加量600mg/L,Pb^2+、Cu^2+去除效率远高于Cd2+、Ni2+;电絮凝反应金属离子去除的最佳pH为7.0,最佳电流密度为1.2~1.8mA/cm^2。混凝与电絮凝金属离子的去除效率与金属离子的半径、相对分子质量大小无关,而与金属离子的溶度积直接相关,金属离子的溶度积越低,混凝和电絮凝去除效率越高。电絮凝较混凝反应具有更高的金属离子去除效率。研究结果对于采用混凝和电絮凝工艺处理多金属污染废水具有借鉴和指导意义。

Research on Co-precipitation Mechanism of Multiple Metal Ions with Coagulation and Electrocoagulation Methods

Coagulation and electrocoagulation methods were applied to remove multiple metal ions (Pb2+, Cd2+, Cu2+, Ni2+) from aqueous solution. Effects of pH value of solution and dosage of coagulant (PAC) on metal ions removal efficiency during coagulation process were explored. Effects of pH value of waste water and current density on metal ions removal efficiency during metal ions electrocoagulation precipitation were comprehensively discussed. The co-precipitation mechanism of multiple metal ions with coagulation and electrocoagulation methods was discovered. The results show that the optimal pH value for Pb2+, Cd2+, Cu2+, Ni2+ removal from aqueous solution with PAC-coagulation is 7.0 and PAC dosage is 600 mg/L. Removal efficiency of Pb2+ and Cu2+ is much higher than that of Cd2+ and Ni2+. While, for multiple metal ions precipitation with electrocoagulation technology, the optimal pH value is 7.0, and suitable current density is 1.2-1.8 mA/cm2. Removal efficiency of metal ions with coagulation and electrocoagulation methods has nothing to do with radius and relative molecular mass of metal ions but is directly related to solubility of metal ions. The smaller the solubility of metal ions is, the higher the removal efficiency is. Compared with coagulation, electrocoagulation has more removal efficiency of metal ions. This project may provide support and guidance for further application of coagulation and electrocoagulation technologies in metallic pollution wastewater treatment.